With a gradual miniaturization of an electronic appliance and a development of a wireless broadcasting/communication technology, a technology for using an electronic appliance such as a notebook or a TV anywhere at anytime is developed. Accordingly, it is required to supply an electronic appliance with a plurality of power sources having different characteristics from one another; convert a power source supply path in order to provide the electronic appliance with a specific power source when the power source is applied thereto; choose a power source among a plurality of power sources when the plurality of power sources are applied to the electronic appliance at the same time; and reliably provide a power source to the electronic appliance regardless of characteristics of the power source applied thereto.
A TV may be classified into a household TV, a portable TV and a vehicle TV. In case of home, a power source is connected to an electronic appliance through an adaptor for transforming an AC power source received from a general power line into a low DC voltage suitable for operating a TV. In case that an appropriate power source cannot be found, a power supply to an electronic appliance may be available by a portable charging battery. Further, in case of a vehicle, a DC power source of the vehicle may be provided to an electronic appliance via a vehicle power source adaptor (so called cigar jack).
Conventionally, a technique for automatically converting an input power source mode of an electronic appliance by automatically detecting an input power source thereof has not been developed though the electronic appliance has been manufactured to use various types of power sources as mentioned above. Accordingly, a user had to convert a power source mode of the electronic appliance manually.
Further, an adaptor power source from a home power line and a battery power source from a charging battery can provide an electronic appliance with a proper voltage suitable for reliably operating the electronic appliance. However, a vehicle cigar jack power source has a drawback that it often supplies an over voltage to an electronic appliance when a vehicle is running in high speed. Accordingly, when an over voltage is generated in a power source output line, it is required to cut off a supply of a power source in order to protect an electronic appliance from over voltage.